Sinker for knitting machines



Nov. 23, 1937. E. R1 PIERCY 2,100,000

SINKER FOR KNITTING MACHINES Filed July 13, 1950 INVENTOR Y 592?; 1 1 /590 ORNEYS the notch-base.

Patented Nov. 23, 1937 UNITED STATES PATENT OFFICE SINKER FOR KNITTING MACHINES Application July 13, 1936, Serial No. 90,356

2 Claims.

My invention relates to the construction of sinkers for knitting machines. It is the object of my invention to provide a sinker which is more accurate in action, has a greater life, and is subject to less wear from the action of the thread and in consequence is less likely to become rough and inaccurate and to cause breakage of the thread.

In a full-fashioned knitting machine for knitting hosiery, the sinkers (by which term I mean here the jack sinkers as distinguished from the dividing sinkers as the dividers are sometimes called) have thread-sinking notches through which the thread slides rapidly much of the time. As a result, there is a very considerable wear at the bottom of the notch; and by reason of that wear and the consequent cutting away of the metal at the bottom of the notch there is produced not only a displacement of the thread from where it should be in machine operation and a consequent lack of uniformity in the knitting but also a roughness which results in catching and breaking the thread and the trouble and delay consequent upon such breakage.

According to my invention I greatly reduce this wear in the notch, and the troubles which come from such wear, by hardening the sinker only at and in the vicinity of the base of the notch, while leaving the remainder of the sinker unhardened so that brittleness and consequent breakage of the sinker as a whole will not be made a concomitant oi the hardening of the notch-base.

Incarrying out my invention, I make the sinker body of a steel which is capable of being hard- .ened by heat treatment; and, while leaving the remainder of the sinker unhardened, I heat the sinker only at and near the notch base, most conveniently by electric current concentrated at that notch-base, and then quench. Because of the thinness of the sinker, quenching in air is usually sufllciently rapid to give the desired hardening at The accompanying drawing illustrates my invention: Fig. 1 is a perspective view of a sinker, with the hardened spot at the notch-base indicated in dotted lines; Fig. 2 is a semi-diagrammatic view showing the electric heating apparatus for the notch-base of the sinker, and the electrical and mechanical connections thereof; Fig. 3 is a plan of the face plate of said heating apparatus, showing the positioning mechanism of the sinker; Fig. 4 is a fragmental enlarged plan showing the general arrangement of the electrodes with respect to the sinker-notch; and Fig. 5 is an under plan of the upper electrodes, showing the arrangement of the wire mesh that underlies the upper electrodes to ensure good contact with the sinker.

The sinker I0 is made of a central body portion provided at its butt with reinforcing mem bers H, as is clear from Fig. 1; and at its threadengaging end is provided with a notch l2 into the base of which the thread is guided by a project'- ing nib or point iii. The wear has come in the past at the base of the notch l3, or in the general area l4 indicated by the dotted line in Fig. 1 around the notch-base.

That wear within the area I4 has in the past caused great difficulty in the machine operation, and has required frequent replacement of sinkers to avoid the breakage and the inaccuracy of operation which continued operation with worn sinkers causes.

According to my invention, I make the body ill of the sinker of a steel which is capable of being hardened by heat treatment. Such a steel, for instance, may be a carbon steel having from 0.60%

to 1.20% carbon. It is not necessary, however,

that the steel be a simple carbon steel.

Such a hardenable steel, by annealing, may be made quite soft and flexible, with no undue brittleness that might tend to cause breakage of the sinker. However, by suitable heat treatment, I harden the area l4, while retaining the bulk of the sinker unhardened.

To obtain this hardening, I may use the apparatus shown in Figs. 2 and 5. In such apparatus, there is a stationary bottom face plate 20 on which the sinker III which is to have its notch-base hardened is placed. That face plate carries two electrodes 2| and 22, mounted in insulation 23 and having their upper ends exposed so that the sinker l0 may lie upon and in contact with them. The two electrodes 2| and 22 are spaced apart, but the spacing between them is considerably less than the width of the sinker l0. Above the stationary bottom face plate 20 is a vertically reciprocable plate 24, which carries two electrodes 25 and 26 suitably mounted in insulation and spaced apart to correspond with the spacing of the electrodes 2i and 22. The electrodes 25 and 26 are in vertical alinement respectively with the electrodes 2| and 22. Normally the plate 24 is raised, so that the space between the upper and lower electrodes is much greater than the thickness of the sinker ID, as is clear from Fig. 2. By suitable operating mechanism, shown as a manually operated bell-crank 21 connected by a link 28 to the plate 24 and having a spring 29 which tends to raise the plate 24, I may depress that plate 24 to bring the electrodes 25 and 26 down upon a sinker it lying upon the electrodes 2i and 22.

The two electrodes 25 and 25 (which form one pair of vertically alined electrodes) are connected to one side 3!; and the two electrodes 22 and 26 (which form another pair of vertically alined electrodes) are connected to the other side 32, of the secondary circuit of a step-down transformer 33. The primary of that step-down transformer 33 is supplied from a main-line supply circuit 3d through a main switch 35; but in series through an additional manually controlled switch 36 an electrically openable switch 37!. The main switch 35 being closed, the closing of the switch 36 completes the circuit through the switch 37 and the primary of the transformer 33; but it also completes a circuit through a solenoid 38 which acts to open the switch 3'! almost immediately after the primary circuit is closed. In this way, only a momentary circuit is completed through the transformer; and the heating secondary current is supplied only momentarily to the sinker lying on the electrodes 2! and 22. A dash-pot 39 may be provided for retarding the opening of the switch 31, and a rheostat 40 may be provided for regulating the strength of the primary current and hence of the secondary or heating current.

The sinker I0 is placed on the electrodes 2! and 22 in about the position shown in Figs. 3 and 4, so that the electrodes 2! and 25 will clamp the sinker on one side of the notch l2 and the electrodes 22 and 26 will clamp the sinker on the other side of such notch. To facilitate the clamping, the two upper electrodes 25 and 26 may be underlaid by strips of fine-mesh wirescreen 4| and 42 respectively, to bear upon. the upper face of the sinker ill on the two sides of the notch l2.

The sinker is so positioned that the current from one pair of vertically alined electrodes to the other must pass through the sinker I 0, and in part swing around the angle formed by the notch I2 to produce a concentration of current at that notch base, and a consequent maximum heat at that point. To facilitate this positioning, the sinker is placed flatwise on the base plate 20 with its normal upper edge 43 and the normal inner edge 44 of its butt bearing against the end and aroaoeo side of a positioning plate having adjusting screws d6 by which it may be adjusted to produce the desired position of the sinker W.

In operation, the sinker i0 is placed on the face plate 28 in proper position so that its notch lies between the electrodes 2i and 22. Then the upper plate 2% is moved down by a proper operation of the manually operated bell-crank 2? to bring the upper electrodes 25 and 26, or rather the wire mesh M or 42 underlying them, down on the upper face of the sinker. Thereupon the switch 36 is closed. That causes a momentary closing of the primary circuit of the transformer 35, and a consequent momentary secondary current passes between one set of vertically alined electrodes to the other through the sinker it. Both the primary and secondary current are only momentary, because the switch 37 is im-' mediately opened and held open to break the primary circuit until the manual switch 35 is again opened.

The secondary current is of such intensity and duration that the sinker at and in the vicinity of the base of the notch I2 is heated above the critical temperature. When the momentary secondary current ceases, the heating likewise ceases, and the heated spot is suddenly cooled by contact with the surrounding metal and air. The cooling is sufiiciently sudden to be a real quenching, even though no liquid quenching medium is used; and is sufiicient to make the base of the notch 92 as hard as desired, even glasshard.

I claim as my invention:

1. A sinker for knitting machines, comprising sinker having at and in the vicinity of the notchbase a spot which has been hardened by heat treatment while the material around that spo is unhardened.

EARL R. PIERCY. 

